Technical, financial and other obstacles must be overcome for hypersonic flight research to progress, a panel of experts said July 11 during the “Transition From Expendable to Reusable Hypersonic Platforms” session at the 2017 AIAA Propulsion and Energy Forum in Atlanta.

“The X-51 proved that we can really do hypersonics,” said David E. Walker, director of the Office of Technology with the Office of Naval Research. “How do we take this and move ourselves forward from these expendable missile type vehicles to reusable aircraft at hypersonic speeds?”

Thomas Jackson, a researcher with experience working on the X-51 Waverider aircraft program and the senior scientist for hypersonics with the Aerospace Systems Directorate at the Air Force Research Laboratory, elaborated on some of the technical hurdles to advancements in the field. He said hypersonic flight speeds are so damaging that every time such a vehicle is flown, it degrades.

“One of the challenges you have in a hypersonic vehicle is you have two systems combined and one has to stop and the other has to start, and there is a point where that transition has to occur,” Jackson said.

Mark Lewis, director of science and technology policy at the Institute for Defense Analyses, pointed to financial and management challenges standing in the way of rapid hypersonic technology advancement.

“The elephant in the room: We don’t fly enough,” he said. “We don’t have enough flight data. Even our programs that are successful, we haven’t had enough opportunity to fly.”

Participants in the panel discussion, "Transition From Expendable to Reusable Hypersonic Platforms,” July 11 at the 2017 AIAA Propulsion and Energy Forum in Atlanta.

The X-51 Waverider, for example, has only been flown four times. Lewis estimates each flight costs about $11 million to $15 million and that running only a tiny number of actual flights works out to be “penny wise, pound foolish” when compared with how much is spent overall.

Colin Tucker, military deputy for the deputy assistant secretary for science, technology, and engineering with the U.S. Air Force, agreed.

“I strongly echo the call for more ground and flight testing,” Tucker said.

Panelists said other issues that have impeded advancement in hypersonic flight research include a lack of urgent practical application for the technology and a lack of stability for researchers in the field.

“Turn times have to be in hours, not in months or years,” Tucker said of the military, adding that end users need a better idea of how they would use hypersonic weapons in a real situation. “We have to flesh out what these weapons will bring to us, not just from a technology standpoint, but as capability.”

Brad Tousley, director of the Tactical Technology Office at DARPA, pointed to challenges in maintaining the workforce and facilities needed to advance the field.

“We need the industrial base to think about the next generation of talent that’s going to work in this area,” Tousley said.